Ousted Catalonian leader Carles Puigdemont and four former ministers have reportedly turned themselves in to Belgian police, The Independent reported.
Belgian state broadcaster VRT said all five have arrived at the Brussels prosecutor's office.
The prosecutor is due to make a statement about a European arrest warrant issued for Mr Puigdemont and the other four as Spain seeks their return for an investigation related to Catalonia's independence bid.
They had fled to Belgium this week after being removed from power by Spanish authorities as part of an extraordinary crackdown to impede the region's illegal declaration of independence.
Federal prosecutors in Belgium had said on Saturday that they were studying the warrants and that they had shared them with city counterparts in Brussels.